|Title||Multiple meltwater discharge and ice rafting events recorded in the deglacial sediments along the Beaufort Margin, Arctic Ocean|
|Publication Type||Journal Article|
|Year of Publication||2019|
|Authors||Klotsko S., Driscoll N., Keigwin L.|
|Journal||Quaternary Science Reviews|
|Type of Article||Article|
|Keywords||amundsen gulf; Arctic Ocean; Beaufort margin; CHIRP; chukchi borderland; dryas; fan development; Geology; glacial lake agassiz; glaciation; Grain size; late pleistocene; mackenzie river; mackenzie river-basin; northwest-territories; Physical Geography; Quaternary; quaternary stratigraphy; sea-level history; Sedimentology-marine cores; seismic reflection; younger|
The first regional model for the deglacial history of the Beaufort margin slope, in the western Arctic, is presented. The conceptual model was developed using new high-resolution CHIRP seismic reflection, multibeam bathymetry, and sediment core data acquired along the margin. This synthesis provides important constraints on sediment source and dispersal patterns for the last deglaciation. The continental slope from Barrow Canyon to the Mackenzie Trough is characterized by thick Holocene sediments mostly sourced from Barrow Canyon and continental discharge. This acoustically transparent, fine-grained unit overlies acoustically laminated sediments sourced from the Mackenzie River and ice rafting. The deglacial history of the margin from Mackenzie Trough to the Amundsen Gulf is characterized by many ice rafting and meltwater discharge events. Ice rafted debris layers were deposited around similar to 14.6 ka and similar to 14.1 ka and likely document enhanced ice shedding events from the Amundsen and M'Clure ice streams as they retreated. There are three inferred meltwater discharge events, all sourced from the Mackenzie region. The oldest discharge event had two phases, one sometime between similar to 14.5 ka and similar to 14.2 ka and another between similar to 14.0 ka and similar to 13.0 ka. This discharge deposited finely laminated sediments more than 7 m thick sourced from proglacial lakes in the area. Following this was a flood event starting at similar to 12.94 ka, which generated high amplitude reflectors, deposited coarse debris, and caused a lowering in the delta O-18 record. This is possibly a major outburst flood from glacial Lake Agassiz with an additional component of Agassiz meltwater that was diverted from its southern drainage pathway down the Mississippi to the Gulf of Mexico. Finally, a third discharge event was initiated by similar to 11.3 ka, which deposited coarse laminated sediments focused in the Mackenzie Trough. Timing of these second and third events correlates with the onset of the Younger Dryas cold period and the preBoreal oscillation event, respectively, suggesting that fresh water discharge may have reached a tipping point, leading to those climate events. (C) 2018 Elsevier Ltd. All rights reserved.
|Short Title||Quat. Sci. Rev.|
Thick, acoustically transparent Holocene sediment imaged from Barrow Canyon to the Mackenzie Trough indicates that discharge down Barrow Canyon and sediment from the Alaskan continent were important sources during this time period, possibly due to rivers reworking glacial sediment exposed by the retreat of glacier ice on the Brooks Range. Acoustically laminated sediments with coarser grain size and higher magnetic susceptibility underlie the Holocene unit. The acoustic reflectivity and thickness of this unit increases towards the Mackenzie Trough, suggesting that it is the main source of the acoustically laminated sediment, in addition to ice-rafted debris (IRD) from the Amundsen and M'Clure ice streams.